Structure and method for stabilizing leads in wire-bonded semiconductor devices

Abstract

A semiconductor device having a leadframe including a pad ( 101 ) surrounded by elongated leads ( 110 ) spaced from the pad by a gap ( 113 ) and extending to a frame, the pad and the leads having a first thickness ( 115 ) and a first and an opposite and parallel second surface; the leads having a first portion ( 112 ) of first thickness near the gap and a second portion ( 111 ) of first thickness near the frame, and a zone ( 114 ) of reduced second thickness ( 116 ) between the first and second portions; the second surface ( 112 a ) of the first lead portions is coplanar with the second surface ( 111 a ) of the second portions. A semiconductor chip ( 220 ) with a terminal is attached the pad. A metallic wire connection ( 230 ) from the terminal to an adjacent lead includes a stitch bond ( 232 ) attached to the first surface of the lead.

We claim: 
     
       1. A leadframe comprising:
 a metallic pad surrounded by a plurality of leads spaced from the metallic pad by a gap, each of the plurality of leads including a first surface and an opposite second surface, the first surface being adapted to connect a bond wire; 
 wherein each of the plurality of leads including a first portion near the gap, a second portion and a third portion separated from the first portion by the second portion, wherein the first portion includes two sections across a width of the lead, a first section with a first thickness and a second section with a second thickness different than the first thickness, the second portion includes the second thickness, and the third portion includes the first thickness. 
 
     
     
       2. The leadframe of  claim 1 , wherein the metallic pad and the plurality of leads include a base metal selected from a group consisting of copper, copper alloys, aluminum, aluminum alloys, iron-nickel alloys, and Kovar. 
     
     
       3. The leadframe of  claim 2 , wherein the first surface includes a layer of nickel plated on the base metal and a layer of palladium plated on the nickel layer, and a layer of gold plated on the palladium layer. 
     
     
       4. The leadframe of  claim 1 , wherein the second portion is offset from the opposite second surface. 
     
     
       5. The leadframe of  claim 1 , wherein a surface of the first section and a surface of the third portion are coplanar. 
     
     
       6. The leadframe of  claim 1 , wherein the second thickness is lesser than the first thickness. 
     
     
       7. The leadframe of  claim 1 , wherein each of the plurality of leads extends to a frame. 
     
     
       8. The leadframe of  claim 1 , wherein the first portion is closer to the metallic pad than the second portion and the third portion. 
     
     
       9. The leadframe of  claim 1 , wherein the first portion is between an end of the lead and a point where the section with the first thickness and the section with the second thickness end, and wherein the third portion is at another end of the lead. 
     
     
       10. A semiconductor device comprising:
 a metallic pad; and 
 a semiconductor chip, attached to the metallic pad, and electrically connected to a first surface of each of a plurality of leads, each of the plurality of leads including an opposite second surface and being spaced from the metallic pad by a gap; 
 wherein each of the plurality of leads including a first portion near the gap, a second portion and a third portion at an end opposite the gap, the second portion between the first portion and the third portion, wherein the first portion includes two sections across a width of the lead, a first section with a first thickness and a second section with a second, different thickness, the second portion includes the second thickness and the third portion includes the first thickness, and wherein the second portion is offset from the opposite second surface. 
 
     
     
       11. The device of  claim 10  wherein the semiconductor chip is electrically connected to the first surface of each of the plurality of leads via wire connections, and wherein the wire connection on the first surface includes a stitch bond. 
     
     
       12. The device of  claim 11  further including a package of a polymeric compound covering portions of the semiconductor chip, wire connection, and at least a portion of each of the plurality of leads. 
     
     
       13. The leadframe of  claim 11 , wherein the wire connection on a surface of the semiconductor chip includes a ball bond. 
     
     
       14. The leadframe of  claim 10 , wherein a surface of the first section and a surface of the third portion are coplanar. 
     
     
       15. The leadframe of  claim 10 , wherein the second thickness is lesser than the first thickness.